Our previous studies based on intraoral dissection of fresh cadavers demonstrated the fissure and loose connective tissues behind the mucosa between the incisivus labii inferioris (ILI) and buccinator (BM) muscles. However, this raised new questions about the relationship among these muscles, the fissure and the buccal space. To our knowledge, no pathway to the oral cavity from the buccal space has been previously demonstrated, although such a pathway would better explain some routes of infection. Therefore, the aim of this study was to clarify the relationship among the mimetic muscles attached to the mandible, the fissure, and the buccal space. Twenty sides from 10 fresh frozen adult cadaveric Caucasian heads were used. The relationships among the ILI, BM, mandible, and buccal space were investigated with dissection and fluoroscopy. In all specimens, the fissure between the lateral border of the ILI and the anterior border of the BM formed the entrance of a space (here termed the bucco‐mandibular space), which corresponded to the buccal mucosa in the premolar region. The superior border of this space was formed by the platysma and associated fascia, which was continuous with the masseteric fascia. This fascia clearly separated this space from the buccal space, which was located lateral to the BM and superior to this space. Clin. Anat. 30:958–962, 2017. © 2017 Wiley Periodicals, Inc.